If you want to know the houseID and unit number of a Nexa switch for example you need to use a sniffer. There are scripts that uses the tellstick to sniff the incoming information, but we made a simple sniffer using an Arduino and a 433MHz reciever – more on that later. (This is the setup we’re using to build custom sensors)

After setting up the config-file just restart the telldus core daemon and you’re good to go.